1. In which war was the famous 'Keep Calm and Carry On' poster used?

2. How many countries are members of the G20 group?

3. Which famous device was initially named the Louisette or Louison?

4. Vicki Vale - one of Batman's love interests in the comics and movies - was based on which Hollywood actress?

5. How do physicists define the force equivalent to 1 newton? 

For the answers, please visit: 10 things I didn't know until last week.